| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power unit which can increase an input voltage range while suppressing the generation of a surge current. SOLUTION: The switching power unit is provided with a transformer 3 which has two primary coils 31A and 31B of the same turns and two inductors Lr1 and Lr2, corresponding to two switching circuits 1 and 2. When DC input voltage Vin is smaller than threshold voltage Vth, a first current path and a second current path are connected in parallel with each other by an input voltage detecting circuit 61, a controller 7, and connection changeover switches S5 and S6. When the DC input voltage Vin is larger than the threshold voltage, they are connected with each other in series. The ratio of turns between the primary coils 31A and 31B and the secondary coils 32A and 32B becomes larger in the case of series connection than parallel connection. Moreover, the current change in the circuit becomes slow by the action of the inductors Lr1 and Lr2. COPYRIGHT: (C)2007,JPO&INPIT
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